Heat exchanger

ABSTRACT

A heat exchanger includes a refrigerant condensing part including tubes and fins. A refrigerant is to flow in the tubes to exchange heat between the refrigerant and an external gas to flow outside the tubes. The fins are connected to the tubes. A gas/liquid separating part is to separate the refrigerant into gas and liquid. A refrigerant supercooling part is to exchange heat between the refrigerant and the external gas. The refrigerant supercooling part includes an inlet and an outlet. The refrigerant is to flow into the refrigerant supercooling part from the inlet. The refrigerant is to flow out of the refrigerant supercooling part from the outlet. The refrigerant flows through the refrigerant condensing part, the gas/liquid separating part, and the refrigerant supercooling part in this order. The external gas flows around the refrigerant supercooling part and then flows around the refrigerant condensing part.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to JapanesePatent Application No. 2010-057192, filed on Mar. 15, 2010, entitled“Heat Exchanger.” The contents of this application are incorporatedherein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchanger.

2. Description of the Related Art

Various different vehicle air conditioners corresponding to differenttypes of vehicles that emit a relatively low amount of heat, such asfuel cell vehicles and electric vehicles are proposed. With such vehicleair conditioners, there is need for improving the ability of the heatpump, and, for example, a known technique proposes a technique ofproviding a supercooling part (subcooling part) downstream of acapacitor (peak) (refer to Japanese Unexamined Patent ApplicationPublication No. 6-341736 (claim 1 and FIG. 1)).

With the technique described in Japanese Unexamined Patent ApplicationPublication No. 6-341736, a refrigerant flows in order through acapacitor and a supercooling part to improve the heat pump capacity.However, the temperature variation in the air received from the heatexchanger has not been considered.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a heat exchangerincludes a refrigerant condensing part, a gas/liquid separating part,and a refrigerant supercooling part. The refrigerant condensing partincludes tubes and fins. A refrigerant is to flow in the tubes toexchange heat between the refrigerant and an external gas to flowoutside the tubes. The fins are connected to the tubes. The gas/liquidseparating part is to separate the refrigerant into gas and liquid. Therefrigerant supercooling part is to exchange heat between therefrigerant and the external gas. The refrigerant supercooling partincludes a supercooling part inlet and an outlet. The refrigerant is toflow into the refrigerant supercooling part from the supercooling partinlet. The refrigerant is to flow out of the refrigerant supercoolingpart from the outlet. The heat exchanger is so constructed that therefrigerant flows through the refrigerant condensing part, thegas/liquid separating part, and the refrigerant supercooling part inthis order. The heat exchanger is so constructed that the external gasflows around the refrigerant supercooling part and then flows around therefrigerant condensing part.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is an exploded perspective view of a heat exchanger according toa first embodiment;

FIG. 2 is an external perspective view of the heat exchanger accordingto the first embodiment;

FIG. 3A is a sectional view of an upper header; and FIG. 3B is asectional view of a lower header;

FIG. 4 is a sectional view of a connecting part of a receiver tank and arefrigerant supercooling part;

FIG. 5 illustrates, in outline, the flow of refrigerant in a heatingmode when the heat exchanger of the first embodiment is applied to avehicle air conditioner;

FIG. 6 illustrates, in outline, the flow of refrigerant in a coolingmode when the heat exchanger of the first embodiment is applied to avehicle air conditioner;

FIGS. 7A and 7B illustrate the effect of the heat exchanger of the firstembodiment, where FIG. 7A illustrates the first embodiment, and FIG. 7Billustrates a comparative example;

FIGS. 8A, 8B, and 8C illustrate a heat exchanger according to a secondembodiment, where FIG. 8A is a partially omitted perspective view, FIG.8B is a sectional view taken along line VIIIB-VIIIB in FIG. 8A, and FIG.8C is s sectional view taken along line VIIIC-VIIIC in FIG. 8A;

FIGS. 9A and 9B illustrate a heat exchanger according to a thirdembodiment, where FIG. 9A is a longitudinal sectional view, and FIG. 9Bis a perspective view of the configuration of a tube;

FIGS. 10A and 10B are sectional views of a connecting part of arefrigerant condensing part, a refrigerant supercooling part, and areceiver tank, where FIG. 10A is a variation, and FIG. 10B is anothervariation; and

FIGS. 11A and 11B illustrate variations in the internal structure of thetube; and FIGS. 11C to 11F illustrate variations in the sectionalstructure of a header.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described with reference tothe drawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings. As illustrated inFIGS. 1 and 2, a heat exchanger 20 according to a first embodimentincludes a refrigerant condensing part 21, a receiver tank (gas/liquidseparating part) 22, and a refrigerant supercooling part 23. Therefrigerant supercooling part 23 is stacked on the refrigerantcondensing part 21.

The refrigerant condensing part 21 includes tubes 21 a extending in thevertical direction arranged at regular intervals and corrugated radiatorfins (fins) 21 b disposed between the tubes 21 a. The tubes 21 a and theradiator fins 21 b are made of a metal having high heat conductivity(radiation performance), such as aluminum or copper.

The refrigerant condensing part 21 includes, in the top area, an upperheader 21 c that distributes a refrigerant discharged from a compressor10, which is described below, to the tubes 21 a and, in the bottom area,a lower header 21 d where the refrigerant that has passed through thetubes 21 a is collected. Details of the upper header 21 c and the lowerheader 21 d will be described below.

A receiver tank 22 is disposed on a side of the refrigerant condensingpart 21 and the refrigerant supercooling part 23 (see FIG. 2) and has afunction (liquid/gas separating function) of separating a refrigerantliquefied by the refrigerant condensing part 21 (liquid refrigerant) anda refrigerant not liquefied (gas refrigerant).

The receiver tank 22 is a vertical cylinder and includes a tank portion22 a that separately retains the liquid refrigerant and the gasrefrigerant. Water contained in the refrigerant introduced to the tankportion 22 a may be removed. In this embodiment, for example, the bottomsurface inside the tank portion 22 a may be covered with a desiccant toremove water.

The refrigerant supercooling part 23 performs heat exchange between theliquid refrigerant from the receiver tank 22 and air-conditioning air(external gas) A to further cool the liquid refrigerant to a completeliquefied.

The refrigerant supercooling part 23 includes a tube 23 a made of thesame material as the refrigerant condensing part 21 and radiator fins 23b that covers the tube 23 a.

The tube 23 a extends horizontally and is bent in a U-shape at both endsof the refrigerant condensing part 21 in a meandering manner from bottomto top.

The radiator fins 23 b are longitudinal plate-liken fins arranged inparallel to cover the periphery of the meandering tube 23 a.

The shape of the radiator fins 21 b of the refrigerant condensing part21 and the radiator fins 23 b of the refrigerant supercooling part 23 isnot particularly limited so long as the air-conditioning air A can passthrough between the radiator fins 21 b of the refrigerant condensingpart 21 and between the radiator fins 23 b of the refrigerantsupercooling part 23. Various modifications may be made. For example,both the radiator fins 21 b and the radiator fins 23 b may be corrugatedfins.

As illustrated in FIG. 3A, there is a space inside the upper header 21 cwhere the refrigerant flows horizontally. The upper ends of the tubes 21a are inserted into through-holes 21 c 1 in the bottom surface of theupper header 21 c to join the upper header 21 c and the tubes 21 a. Inthis way, the refrigerant is guided from the compressor 10 to the upperheader 21 c are distributed to the tubes 21 a, as indicted by thearrows, and flows downward.

As illustrated in FIG. 3B, there is a space inside the lower header 21 dwhere the refrigerant flows horizontally. The lower ends of the tubes 21a are inserted into through-holes 21 d 1 in the upper surface of thelower header 21 d to join the tubes 21 a and the lower header 21 d.

The lower header 21 d is connected to the receiver tank 22 via a pipe 22b. The pipe 22 b penetrates the bottom of the tank portion 22 a upwardinto the tank portion 22 a by a predetermined length. The predeterminedlength is preferably set to a length that the liquid surface of theretained refrigerant does not exceed the tip (upper edge) of the pipe 22b. In FIG. 3A, the predetermined length appears shorter than it actuallyis for the sake of description.

The lower header 21 d is connected to a capacitor 30, which is describedbelow, via a pipe a2 that extends away from the receiver tank 22 (seeFIG. 6). In this embodiment, the lower header 21 d constitutes abranching channel.

As illustrated in FIG. 4, the refrigerant supercooling part 23 isconnected to the receiver tank 22 via a pipe 22 c. The pipe 22 c extendsdownward from the bottom of the receiver tank 22 and is connected to aninlet 23 a 1 (introducing part 23 c) of the tube 23 a of the refrigerantsupercooling part 23.

The heat exchanger 20 having such a configuration can be used as avehicle air conditioner 1A of a vehicle V, such as an electric vehicle(EV), a fuel cell vehicle (FCV), or a hybrid electric vehicle (HEV).

As illustrated in FIGS. 5 and 6, the vehicle air conditioner 1A includesthe compressor 10, the heat exchanger 20, the capacitor 30, an automaticexpansion valve 40, a first evaporator 50, a second evaporator 60, acooler/heater switching unit 70, and an electronic control unit (ECU)80.

The compressor 10 is driven by a motor (or an engine) to take in andcompress a refrigerant, and discharge a high-temperature, high-pressurerefrigerant to the heat exchanger 20.

The capacitor 30 includes a condensing part 31 and a receiver tank 32and is disposed inside the front hood of the vehicle V. The refrigerantflowing through the condensing part 31 exchanges (radiates) heat with(to) the outside air introduced through the front of the vehicle V. Thecondensing part 31 includes a plurality of tubes (not shown) extendingtransversely and radiator fins (not shown).

The receiver tank 32 is disposed on one side of the condensing part 31and is shaped as a cylinder, such as that of the receiver tank 22. Thereceiver tank 32 has a function (liquid/gas separating function) ofseparating the liquid refrigerant and the gas refrigerant in thecondensing part 31 during cooling.

The opening of the automatic expansion valve 40 can be changed inaccordance with the refrigerant temperature. The automatic expansionvalve 40 includes a detector (not shown) that detects the temperatureand pressure of the refrigerant that flowed out from the firstevaporator 50 (or second evaporator 60), which is described below. Theopening of the automatic expansion valve 40 is changed in accordancewith the temperature and pressure of the refrigerant that flowed outfrom the first evaporator 50 (or second evaporator 60) to change theflow rate of the refrigerant.

The refrigerant flowing through the first evaporator 50 exchanges heatwith the air-conditioning air A (heat source) discharged from thevehicle interior C. The first evaporator 50 is disposed in the reararea, such as a luggage compartment D (trunk), of the vehicle V wherethe air-conditioning air A is discharged outside the vehicle. The firstevaporator 50 takes in heat from the air-conditioning air A (heatsource) discharged from the vehicle interior C of the vehicle V to theoutside of the vehicle through the refrigerant during heating. The heatsource is not limited to the air-conditioning air A discharged from thevehicle interior C, and instead, exhaust heat from the driving part (forexample, the motor) of the vehicle V may be used.

The second evaporator 60 is disposed in the vehicle interior C andperforms heat exchange between the refrigerant and the air-conditioningair A. The second evaporator 60 is disposed upstream of the heatexchanger 20 along the flow of the air-conditioning air A.

A refrigerant discharge port 10 b of the compressor 10 is connected to arefrigerant inlet 21 a 1 of the refrigerant condensing part 21 via apipe a1, and a refrigerant outlet 21 a 2 of the refrigerant condensingpart 21 is connected to a refrigerant inlet 30 a of the capacitor 30 viaa pipe a2, which has an electromagnetic valve V1. The electromagneticvalve V1 constitutes a capacitor blocking unit that blocks the flow ofthe refrigerant to the capacitor 30 by closing.

A refrigerant outlet 30 b of the capacitor 30 is connected to adecompression-side inlet 40 a of the automatic expansion valve 40 via apipe a3 having a check valve V2. A decompression-side outlet 40 b of theautomatic expansion valve 40 is connected to a refrigerant inlet 50 a ofthe first evaporator 50 via a pipe a4. The check valve V2 restricts onlythe flow of the refrigerant from the capacitor 30 to the automaticexpansion valve 40.

A refrigerant outlet 50 b of the first evaporator 50 is connected to arefrigerant inlet 60 a of the second evaporator 60 via a pipe a5. Arefrigerant outlet 60 b of the second evaporator 60 is connected to atemperature-detection-side inlet 40 c of the automatic expansion valve40 via a pipe a6. A temperature-detection-side outlet 40 d of theautomatic expansion valve 40 is connected to a refrigerant suction port10 a of the compressor 10 via a pipe a7.

An outlet 23 a 2 of the refrigerant supercooling part 23 of the heatexchanger 20 merges with the pipe a3 between the check valve V2 and theautomatic expansion valve 40 via a pipe a8 having, in order from theupstream side, an electronic valve V3, a middle aperture S, and a checkvalve V4. The check valve V4 restricts only the flow of the refrigerantfrom the refrigerant supercooling part 23 to the automatic expansionvalve 40. The electronic valve V3 constitutes a supercoolingcircumvention unit through which the refrigerant flow to circumvent therefrigerant supercooling part 23 by closing.

The pipe a3 between the outlet 30 b of the capacitor 30 and the checkvalve V2 merges with the pipe a7 via a pipe a9 having, in order from theupstream side, an electronic valve V5 and a check valve V6. The checkvalve V6 restricts only the flow of the refrigerant from the pipe a3 tothe pipe a7.

A pipe a10 having an electronic valve V7 functions as a first-evaporatorcircumvention unit and connects the pipe a4 and the pipe a5.

A pipe all having an electronic valve V8 functions as asecond-evaporator circumvention unit and connects the pipe a5 and thepipe a6.

The cooler/heater switching unit 70 switches the flow of the refrigerantand the air-conditioning air A during heating and the flow of therefrigerant and the air-conditioning air A during cooling. Thecooler/heater switching unit 70 includes the first-evaporatorcircumvention unit, the second-evaporator circumvention unit, thecapacitor circumvention unit, the supercooling circumvention unit, andan air damper 71.

The air damper 71 is disposed in a space between the heat exchanger 20and the second evaporator 60. In a heating mode, the air damper 71 isopened to pass the air-conditioning air A introduced from outside thevehicle to the vehicle interior C through the second evaporator 60 andthrough the heat exchanger 20 (see FIG. 5). In contrast, in a coolingmode, the air damper 71 is closed to prevent the air-conditioning air Aintroduced to the vehicle interior C from passing through the secondevaporator 60 and the heat exchanger 20 (see FIG. 6).

The ECU 80 controls the opening and closing of the electromagneticvalves V1, V3, V5, V7, and V8 and controls the opening and closing ofthe air damper 71 to control the flow of the refrigerant and the flow ofthe air-conditioning air A during heating and cooling.

Next, the operation of the vehicle air conditioner 1A will be described.The vehicle V illustrated in FIG. 5 is in a heating mode, and theelectromagnetic valves V1 and V7 are closed. The vehicle V illustratedin FIG. 6 is in a cooling mode, and the electronic valves V3, V5, and V8are closed.

Operation in Heating Mode

As illustrated in FIG. 5, in a heating mode, when the compressor 10 isdriven, the refrigerant sucked in through the suction port 10 a of thecompressor 10 and discharged from the discharge port 10 b is suppliedthrough the pipe a1 to the heat exchanger 20. In this way, ahigh-temperature, high-pressure refrigerant (gas) is supplied to theheat exchanger 20.

The refrigerant supplied from the compressor 10 is introduced to therefrigerant condensing part 21 of the heat exchanger 20 and exchangesheat with the air-conditioning air A introduced from outside the vehicleto the vehicle interior C while flowing through the refrigerantcondensing part 21 from top to bottom (see FIG. 1). The refrigerant iscooled and condensed by the air-conditioning air A (cold outside air) tochange the high-temperature gas refrigerant to a low-temperature liquidrefrigerant. The temperature of the air-conditioning air A is raised bythe heat emitted during condensation.

The refrigerant (liquid refrigerant) from the refrigerant condensingpart 21 is introduced to the receiver tank 22 through the pipe 22 b. Atthe receiver tank 22, the refrigerant is separated into gas and liquid,i.e., the liquid refrigerant accumulates in the bottom area of the tankportion 22 a (see FIG. 1), and the gas refrigerant that was notliquefied at the refrigerant condensing part 21 accumulates in the toparea of the tank portion 22 a. The liquid refrigerant separated at thereceiver tank 22 is sent from the bottom of the receiver tank 22 throughthe pipe 22 c to the refrigerant supercooling part 23.

The refrigerant (liquid refrigerant) introduced to the introducing part23 c at the lower edge of the refrigerant supercooling part 23 exchangesheat with the air-conditioning air A (cold outside air) introduced tothe vehicle interior C. Since the refrigerant supercooling part 23 ispositioned upstream (windward) of the refrigerant condensing part 21with respect to the flow of the air-conditioning air A, the refrigerantis further cooled by the air-conditioning air A and becomes a liquidrefrigerant having a temperature lower than the condensationtemperature. The processing carried out in a subcooled state.

The liquid refrigerant from a deriving part 23 d disposed at the upperedge of the refrigerant supercooling part 23 passes through the middleaperture S, where it is decompressed.

The liquid refrigerant decompressed at the middle aperture S isintroduced to the automatic expansion valve 40 through the pipe a3. Thedecompressed liquid refrigerant becomes a mixture of liquid and gas atthe automatic expansion valve 40 and is then introduced to the firstevaporator 50.

The first evaporator 50 performs heat exchange between theair-conditioning air A discharged from the vehicle interior C to theluggage compartment D (see FIG. 5) and the refrigerant. The refrigerantabsorbs heat from the air-conditioning air A and evaporates while itpasses through the first evaporator 50. In this way, the heat of thevehicle interior C can be efficiently used.

The refrigerant from the first evaporator 50 passes through a pipe allthat circumvents the second evaporator 60 and then passes through thepipe a6, the automatic expansion valve 40, and the pipe a7 to return tothe compressor 10.

In the vehicle air conditioner 1A in a heating mode, the ECU 80 fullyopens the air damper 71 to allow the air-conditioning air A took in fromoutside the vehicle to pass through both the second evaporator 60 andthe heat exchanger 20. Since the refrigerant circumvents the secondevaporator 60, heat exchange is not performed at the second evaporator60. At the heat exchanger 20, the air-conditioning air A is heated bythe high-temperature, high-pressure refrigerant by heat emission at therefrigerant condensing part 21. As a result, warm air is introduced tothe vehicle interior C.

In heating mode, the electronic valve V5 is opened by the ECU 80 suchthat the capacitor 30 and the suction port 10 a of the compressor 10communicate through the pipe a9. In this way, the suction force(negative pressure) generated at the suction port 10 a when thecompressor 10 is operated sucks the refrigerant (liquid refrigerant)remaining in the capacitor 30, such as in the receiver tank 32, throughthe pipe a9. Accordingly, the refrigerant can be efficiently used.

Operation in Cooling Mode

As illustrated in FIG. 6, when the compressor 10 is driven in a coolingmode, the refrigerant compressed at the compressor 10 is suppliedthrough the pipe a1 to the heat exchanger 20. In this way, thehigh-temperature, high-pressure refrigerant (gas) is supplied to theheat exchanger 20.

The refrigerant supplied from the compressor 10 is introduced to therefrigerant condensing part 21 of the heat exchanger 20. However, sincethe air damper 71 is fully closed, heat is not exchanged with theair-conditioning air A even when the refrigerant flows through therefrigerant condensing part 21. Therefore, the air-conditioning air A isnot heated by the high-temperature, high-pressure refrigerant. Since theECU 80 opens the electromagnetic valve V1 and closes the electronicvalve V3, the refrigerant that has passed through the refrigerantcondensing part 21 is introduced to the capacitor 30 through the pipea2, without flowing through the receiver tank 22 and the refrigerantsupercooling part 23.

The refrigerant introduced to the capacitor 30 is cooled by exchangingheat with the outside air while it passes through the condensing part31. The refrigerant after heat exchange is separated into gas and liquidin the receiver tank 32 to separate the liquid refrigerant. The liquidrefrigerant in the receiver tank 32 is introduced to the automaticexpansion valve 40 through the pipe a3.

The liquid refrigerant introduced to the automatic expansion valve 40 isdecompressed to a mixture of liquid refrigerant and gas refrigerant. Therefrigerant that passed through the automatic expansion valve 40 passesthrough the pipe a10 that circumvents the first evaporator 50 and isintroduced to the second evaporator 60.

At the second evaporator 60, the air-conditioning air A is cooled byheat exchange between the air-conditioning air A introduced to thevehicle interior C and the refrigerant, i.e., by the low-temperaturerefrigerant cooled by the capacitor 30 absorbing heat from theair-conditioning air A while passing through the second evaporator 60,and the cooled air-conditioning air A is introduced to the vehicleinterior C.

The refrigerant from the second evaporator 60 returns to the compressor10 through the pipe a6, the automatic expansion valve 40, and the pipea7.

Since the air damper 71 is fully closed in the vehicle air conditioner1A in a cooling mode, the air-conditioning air A cooled at the secondevaporator 60 is not heated at the heat exchanger 20. As a result, coldair is introduced to the vehicle interior C.

In a dehumidification heating mode, unlike in a heating mode, the ECU 80closes the electronic valve V8 so that the refrigerant passes throughthe second evaporator 60. Steps in the operation that are the same asthose in a heating mode will not be repeated.

The refrigerant introduced from the first evaporator 50 to the secondevaporator 60 absorbs heat from the air-conditioning air A, and as aresult, the air-conditioning air A is cooled. Then, the refrigerant fromthe second evaporator 60 returns to the compressor 10 through the pipea6, the automatic expansion valve 40, and the pipe a7.

In this way, in a dehumidification heating mode, the second evaporator60, where heat exchange is performed between the refrigerant from thefirst evaporator 50 and the air-conditioning air A, cools theair-conditioning air A by the refrigerant flowing into the secondevaporator 60 absorbing heat. Consequently, dehumidification isperformed to remove the water vapor contained in the air took in fromoutside (air-conditioning air A).

As described above, in the heat exchanger 20 according to the firstembodiment, by extending the tubes 21 a vertically to provide a downwardstream of the refrigerant flowing through the refrigerant condensingpart 21 and by providing the refrigerant introducing part 23 c in thelower area of the refrigerant supercooling part 23 and the refrigerantderiving part 23 d in the upper area to provide a upward stream of therefrigerant, the temperature of the refrigerant is lowered from top tobottom in the refrigerant condensing part 21, and the temperature of therefrigerant is lowered from bottom to top in the refrigerantsupercooling part 23. Therefore, the temperature of the gas dischargedfrom the refrigerant condensing part 21 can be uniform.

In the heat exchanger 20 according to the first embodiment, by providingan overheating region R1 at a refrigerant inlet Q1 of the refrigerantcondensing part 21 (see FIG. 3A) and a supercooling region R2 at arefrigerant outlet Q2 of the refrigerant supercooling part 23 (seeFIG. 1) and letting the air-conditioning air A flow through thesupercooling region R2 and then through the overheating region R1, thefollowing advantages are achieved.

As illustrated in FIG. 7A, when the cold air-conditioning air A isintroduced from outside the vehicle to the refrigerant supercooling part23, a refrigerant cooled at the refrigerant supercooling part 23 andhaving a temperature lower than the condensation temperature flowsthrough the supercooling region R2, and a (gaseous) refrigerant from thecompressor 10 having a temperature higher than the condensationtemperature flows through the overheating region R1. Therefore, theair-conditioning air A received from the refrigerant condensing part 21at the height of the supercooling region R2 and the overheating regionR1 turns into warm wind (gas) with a predetermined temperature (forexample, Ta). A refrigerant that has just been introduced to therefrigerant supercooling part 23 and has a temperature close to thecondensation temperature flows through a region R3 on the refrigerantinlet side of the refrigerant supercooling part 23, and a refrigerantthat has released heat at the refrigerant condensing part 21 and has atemperature close to the condensation temperature flow through a regionR4 on the refrigerant outlet side of the refrigerant condensing part 21.Therefore, the air-conditioning air A received from the refrigerantcondensing part 21 at the height of the regions R3 and R4 turns intowarm wind (gas) having a temperature Ta, similar to that describedabove.

For comparison, as illustrated in FIG. 7B, when the air-conditioning airA is passed only through the refrigerant condensing part 21, arefrigerant having a temperature higher than the condensationtemperature flows through a region R10 on the refrigerant inlet side,and, as a result, the air-conditioning air A received from therefrigerant condensing part 21 becomes hot; since a refrigerant having atemperature close to the condensation temperature flows through a regionR20 on the refrigerant outlet side, the air-conditioning air A receivedfrom the refrigerant condensing part 21 becomes warm. Consequently,there is a temperature variation along the vertical direction of therefrigerant condensing part 21.

By letting the same air-conditioning air A flow through the overheatingregion R1 provided at the refrigerant inlet Q1 of the refrigerantcondensing part 21 and the supercooling region R2 provided at therefrigerant outlet Q2 of the refrigerant supercooling part 23,temperature variation in other regions can be prevented, and stable heatexchange can be achieved. Here, “the same air-conditioning air Aflow[ing] through” means the air-conditioning air A that exchanged heatwith the refrigerant flowing through the supercooling region R2exchanges heat with the refrigerant flowing through the overheatingregion R1.

In the heat exchanger 20 according to the first embodiment, asillustrated in FIG. 3B, since the lower header 21 d of the refrigerantcondensing part 21 is a branching channel, by closing the electronicvalve V3 (see FIG. 6) in a cooling mode, the refrigerant that passedthrough the tubes 21 a flows into the capacitor 30, without flowing intothe receiver tank 22. In contrast, in a heating mode, by closing theelectromagnetic valve V1 (see FIG. 5), the refrigerant that passedthrough the tubes 21 a flows to the receiver tank 22, without beingdirected to the capacitor 30, and is introduced to the automaticexpansion valve 40 through the refrigerant supercooling part 23. In thisway, in a cooling mode, the refrigerant is prevented from flowing intothe receiver tank 22 and the refrigerant supercooling part 23.

FIGS. 8A, 8B, and 8C illustrate a heat exchanger 200 according to asecond embodiment. FIG. 8A is a partially omitted perspective view; FIG.8B is a sectional view taken along line VIIIB-VIIIB in FIG. 8A; and FIG.8C is a sectional view taken along line VIIIC-VIIIC in FIG. 8A. The heatexchanger 200 according to the second embodiment is an integrated unitof tubes constituting a refrigerant condensing part and tubesconstituting a refrigerant supercooling part.

As illustrated in FIG. 8A, the heat exchanger 200 includes a pluralityof tubes 210 extending in the vertical direction, radiator fins 220disposed between the tubes 210, an upper header 230, and a lower header240. Since the receiver tank 22 is the same as that according to thefirst embodiment, the same reference numeral is used, and descriptionthereof is not repeated.

As illustrated in FIG. 8C, the tubes 210 each includes a substantiallyoval cylinder 211 and a partition 212 that divides the space inside thecylinder 211 into two sections. The partition 212 extends verticallyfrom the upper edge to the lower edge of the tube 210 to divide thespace inside the tube 210 into two sections. The upper edge 213 of thecylinder 211 has notches 214 at positions corresponding to the partition212. The lower edge 215 of the cylinder 211 also has notches 216 atpositions corresponding to the partition 212 (see FIG. 8B).

The radiator fins 220 are corrugated fins and are disposed entirelyalong both sides of the tube 210 (see FIG. 8A).

As illustrated in FIG. 8B, the upper header 230 as a substantiallyconvex cross-section with respect to the flow of the refrigerant. Theupper header 230 includes a base 231 to which the tube 210 is connected,a cover 232 that covers the top of the base 231, and a partition 233that partitions the space inside the upper header 230 at a positioncorresponding to the partition 212.

The base 231 has a substantially plate-like form extending in the samedirection as the tubes 210. Through-holes 231 a into which the upperedges 213 of tubes 210 are inserted are formed at positionscorresponding to the tubes 210. The cover 232 has a convex shape andblocks the upper section of the base 231 and one of the ends on thereceiver tank 22 side. The partition 233 extends in the alignmentdirection of the tube 210. The lower edges of the partition 233 contacta notch 214.

The base 231, the cover 232, and the partition 233 configured in thisway are joined together by, for example, welding. The channelcross-section of a channel S10 of a tube 210 disposed leeward of theair-conditioning air A is larger than the channel cross-section of achannel S20 of a tube 210 disposed windward of the air-conditioning airA. In the upper header 230, the channel cross-section of a channel S1corresponding to the channel S10 is larger than the channelcross-section of a channel S3 corresponding to the channel S20.Similarly, in the lower header 240, the channel cross-section of achannel S2 corresponding to the channel S10 is larger than the channelcross-section of a channel S4 corresponding to the channel S20.

The lower header 240 has a configuration similar to the upper header 230in that it includes a base 241 having through-holes 241 a in which thelower ends of the tubes 210 are inserted, a cover 242 that covers thebase 241, and a partition 243. An end surface 240 a of the lower header240 on the receiver tank 22 side is connected to a pipe 22 b thatcommunicates with the channel S2 and a pipe 22 c that communicates withthe channel S4.

In the heat exchanger 200 having such a configuration, in a heatingmode, the refrigerant from the compressor 10 passes through the channelS1 of the upper header 230, the channel S10 of the tube 210, and thechannel S2 of the lower header 240 to heat the air-conditioning air A.The refrigerant that exchanged heat with the air-conditioning air A isintroduced to the receiver tank 22, where liquid and gas is separated,through the pipe 22 b and is introduced to the channel S4 of the lowerheader 240 through the pipe 22 c. Then, the refrigerant is introduced tothe automatic expansion valve 40 (middle aperture S) through thechannels S20 of the tubes 210 and the channel S3 of the upper header230.

Accordingly, in the heat exchanger 200 according to the secondembodiment, the refrigerant condensing part 21 is constituted of thechannels S10 of the tubes 210, the radiator fins 220, the channel S1 ofthe upper header 230, and the channel S2 of the lower header 240. In thesecond embodiment, the refrigerant supercooling part is constituted ofthe channels S20 of the tubes 210, the radiator fins 220, the channel S3of the upper header 230, and the channel S4 of the lower header 240.

As illustrated in FIG. 8B, in the heat exchanger 200 according to thesecond embodiment having such a configuration, the same air-conditioningair A flows through the overheating region R1 at the refrigerant inletQ1 of the refrigerant condensing part and the supercooling region R2 atthe refrigerant outlet Q2 of the refrigerant supercooling part.Therefore, air-conditioning air A having a similar temperature can bereceived from other regions, and stable heat exchange without atemperature variation can be achieved.

According to the second embodiment, since the lower header 240constitutes the channel S2 (branching channel) that branches into thechannel through the receiver tank 22 and the channel through thecapacitor 30, in a cooling mode, the refrigerant can be prevented fromflowing through the receiver tank 22 and the refrigerant supercoolingpart.

FIGS. 9A and 9B illustrate a heat exchanger 300 according to a thirdembodiment. FIG. 9A is a longitudinal sectional view; and FIG. 9B is aperspective view of the configuration of a tube. In the heat exchanger300 according to the third embodiment, tubes 310 constituting arefrigerant condensing part and tubes 320 constituting a refrigerantsupercooling part are different types of tubes.

The heat exchanger 300 includes the vertically-extending tubes 310 and320, radiator fins 330 disposed between the tubes 310 and 320, an upperheader 340, and a lower header 350.

As illustrated in FIG. 9B, the channel of a tube 310 is shaped as half aracetrack, and the channel of a tube 320 is shaped as a half oval. Theflat wall surface of a tube 310 and the flat wall surface of a tube 320face each other and a gap 360 is provided therebetween.

The upper header 340 differs from the upper header 230 of the secondembodiment in that the base 341 has through-holes 341 a and 341 b intowhich the upper ends of the tubes 310 and 320 are respectively inserted.The lower header 350 differs from the lower header 240 of the secondembodiment in that the base 351 has through-holes 351 a and 351 b intowhich the upper ends of the tubes 310 and 320 are respectively inserted.

In the third embodiment, the tubes 310, the radiator fins 330, thechannel S1 of the upper header 340, and the channel S2 of the lowerheader 350 constitute a refrigerant condensing part. In the thirdembodiment, the tubes 320, the radiator fins 330, the channel S3 of theupper header 340, and the channel S4 of the lower header 350 constitutea refrigerant supercooling part 23.

The heat exchanger 300 according to the third embodiment having such aconfiguration, similar to the first and second embodiments, can achievestable heat exchange without a temperature variation, and in a coolingmode, the refrigerant can be prevented from flowing to the receiver tank22 and the refrigerant supercooling part.

In the second embodiment, the lower header 240 and the receiver tank 22are connected with the pipes 22 b and 22 c. This, however, is notlimited, and, as illustrated in FIG. 10A, a block member 400 having achannel 401 connecting the channel S2 of the lower header 240 and thereceiver tank 22 and a channel 402 connecting the channel S4 of thelower header 240 and the receiver tank 22 may be used instead. Asillustrated in FIG. 10B, the lower header 240 may extend to the bottomof the receiver tank 22; the pipe 22 b in the receiver tank 22 may beconnected to a communicating hole 245 in the upper surface of thereceiver tank 22; and the opening of an outlet of the receiver tank 22may be connected to a communicating hole 246 in the upper surface. Theconfiguration illustrated in FIGS. 10A and 10B may also be applied tothe first and third embodiments.

The tubes 21 a, 23 a, 210, 310, and 320 in the embodiments of thepresent invention are not limited to simple cylinders. Instead, forexample, as illustrated in FIGS. 11A and 11B, a plurality of channelsmay be provided inside tubes 210A, 310A, and 320A by embedding aplurality of partitions s. The partition 212 illustrated in FIG. 8C maybe used together with the partition s in the tube 210A illustrated inFIG. 11A.

In the headers 230 and 240 illustrated in FIGS. 8A, 8B, and 8C and theheaders 340 and 350 illustrated in FIGS. 9A and 9B, the partition andcover may be provided as an integrated unit, as represented by referencenumeral 230A in FIG. 11C. As represented by reference numeral 230B inFIG. 11D, the cover, base, and partition may be provided as anintegrated unit. As represented by reference numeral 230C in FIG. 11E, aconvex header h1 on the refrigerant condensing part side and a convexheader h2 on the refrigerant supercooling part side may be connected attheir opposing sides, and the contact surface of the headers h1 and h2may constitute a partition. As represented by reference numeral 230D inFIG. 11F, a sealing member t may be applied at in contact area.

According to the embodiment of the present invention, by extending thetubes vertically and providing a deriving part and an introducing partat the top and bottom of the refrigerant supercooling part, thedirection of the refrigerant flowing through the refrigerant condensingpart and the direction of the refrigerant flowing through therefrigerant supercooling part becomes opposite, and, as a result, thetemperature of the gas received from the heat exchanger becomes uniform.

That is, by the refrigerant flowing from top to bottom in therefrigerant condensing part, the gas is cooled by the refrigerantemitting heat and the condensed refrigerant (liquid refrigerant)accumulates at the bottom, whereas, by the refrigerant (liquidrefrigerant) flowing from the introducing part at the bottom to thederiving part at the top, the gas is cooled even more by heat emissionof the refrigerant. In this way, the temperature of the refrigerantdecreases from the top to the bottom in the refrigerant condensing partand from the bottom to top in the refrigerant supercooling part, atemperature variation along the vertical direction of the heat exchangercan be prevented.

According to the embodiment of the present invention, for example, arefrigerant having a temperature higher than the condensationtemperature flows through the overheating region at the refrigerantinlet, and a refrigerant having a temperature lower than thecondensation temperature flows through the supercooling region at therefrigerant outlet. Therefore, the refrigerant discharged from the heatexchanger is a gas having an intermediate temperature close to thecondensation temperature. By disposing an overheating region and asupercooling region, as described above, gas having no temperaturevariation in the vertical direction of the heat exchanger can beobtained. In this way, stable heat exchange is possible.

According to the embodiment of the present invention, by providing thebranching channel upstream of the gas/liquid separating part, when therefrigerant does not have to flow through the gas/liquid separating partand the refrigerant supercooling part in cooling mode, the refrigerantcan be prevented from flowing to the gas/liquid separating part side.

The embodiment of the present invention provides a heat exchangerpreventing temperature variation in air received from the heatexchanger.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

1. A heat exchanger comprising: a refrigerant condensing part comprising: tubes in which a refrigerant is to flow to exchange heat between the refrigerant and an external gas to flow outside the tubes; and fins connected to the tubes; a gas/liquid separating part to separate the refrigerant into gas and liquid; and a refrigerant supercooling part to exchange heat between the refrigerant and the external gas, the refrigerant supercooling part comprising: a supercooling part inlet from which the refrigerant is to flow into the refrigerant supercooling part; and an outlet from which the refrigerant is to flow out of the refrigerant supercooling part, wherein the heat exchanger is so constructed that the refrigerant flows through the refrigerant condensing part, the gas/liquid separating part, and the refrigerant supercooling part in this order, and wherein the heat exchanger is so constructed that the external gas flows around the refrigerant supercooling part and then flows around the refrigerant condensing part.
 2. The heat exchanger according to claim 1, wherein the refrigerant condensing part includes a condensing part inlet from which the refrigerant is to flow into the tubes, wherein an overheating region is disposed around the condensing part inlet of the refrigerant condensing part, and a supercooling region is disposed around the outlet of the refrigerant supercooling part, and wherein the heat exchanger is so constructed that the external gas flows through the supercooling region and then, at least part of the external gas flows through the overheating region.
 3. The heat exchanger according to claim 1, wherein the refrigerant condensing part includes a branching channel to branch into a first channel connected to the gas/liquid separating part and a second channel from which the refrigerant is to flow out of the refrigerant condensing part.
 4. The heat exchanger according to claim 2, wherein the refrigerant condensing part includes a branching channel to branch into a first channel connected to the gas/liquid separating part and a second channel from which the refrigerant is to flow out of the refrigerant condensing part. 